Condylar-mandibular asymmetry, a reality.

The aim of this study is to evaluate the possibility to recognize a condylar-mandibular asymmetry through a panoramic radiograph. Results from a previous work, in which 100 skulls from the Museum of the Institute of Anatomy of the University of Pavia were studied and measured, showed the presence of asymmetry. Using the same skulls we examined the possible correlation between morphological and radiological data. We did not find out correlation's between the condylar asymmetry evaluated at the anatomical level and the radiological asymmetry which was indeed found. This is probably due to the different positioning of the jaws during the two different measuring processes. Nevertheless our results confirm the daily experience of dentistry: asymmetry of mandibular condyle can be one of the mayor causes for the asymmetry of the stomatognatic apparatus.

Craniomandibular stiffness in myogenous and arthrogenous CMD patients, and control subjects: a clinical and experimental investigation.

The purpose of this study was to compare active maximum mouth opening, endfeel distance, and craniomandibular stiffness values of three craniomandibular disorder (CMD) patient subgroups and a control group. The CMD patient subgroups consisted of myogenous pain patients and arthrogenous pain patients with a 'closed lock' and arthrogenous pain patients without a 'closed lock'. Both myogenous pain patients and the 'closed lock' patients showed great differences on all parameters (P < 0.05-P < 0.001). However, the arthrogenous pain patients without a 'closed lock' revealed no statistical differences with the control group on any of the tested parameters.

EMG differences between weak and strong myogenous CMD patients and healthy controls.

Electromyographic and clinical characteristics of 42 myogenous craniomandibular disorder (CMD) patients were related to 40 healthy control subjects. Surface EMG recordings were obtained from the masseter and the temporal muscles. The clinical examination included active maximum mouth opening, endfeel distance, active laterotrusion and lateral endfeel distance, dental abrasion, the presence of a lateral slide (RCP-ICP) and the amount of static pain. Orthopantomographic X-rays were available from 32 CMD patients for measuring the condylar and ramus asymmetry. Compared to the control group lower masseter and temporal EMG amplitudes were found for myogenous CMD patients (P < 0.001). When the activity of the temporal muscle was compared with the activity of the masseter muscle, the CMD patients showed proportionally higher temporal muscle activities than the controls (P < 0.05, 50% clenching level). CMD patients also showed smaller mandibular excursions, larger endfeel distances and more dental abrasion than controls. The temporal muscle asymmetries showed significant negative correlations with the ramus asymmetries. The lower and upper quartile of the distribution of the mean masseter EMG amplitudes were used to distinguish weak and strong muscles in patients and controls. Weak patients showed proportionally high temporal muscle activities, larger masseter and temporal muscle asymmetries, and larger endfeel distances compared to strong CMD patients. These differences were not found between weak and strong controls. In conclusion, it can be said that the electromyographic and clinical findings of the myogenous CMD patients suggest a functional difference between weak and strong patients and indicate the need for more individually designed treatment modalities for functional muscle and joint CMD problems.

The temporal/masseter co-contraction: an electromyographic and clinical evaluation of short-term stabilization splint therapy in myogenous CMD patients.

The short-term effect (3-6 weeks) of the use of a stabilization splint was investigated in a group of 35 myogenous craniomandibular disorder patients. The patients were clinically examined and surface EMG recordings of the temporal and masseter muscles were made during clenching in the intercuspal position (ICP), immediately after the insertion of the splint (SSP), and after at least 3 weeks of splint treatment (SSP 3). With the use of the error variance of the activity index changes in EMG activity were investigated. Three groups of patients were then recognized. One group showed a decrease in temporal muscle activity during splint treatment. Another group did not show any significant change during splint treatment. The third group showed an increase of temporal muscle activity. In general, significant reductions in the amount of static pain were found. In the group with a significant reduction of temporal muscle activity (n = 15) there was a greater decrease in the amount of static pain (P < 0.05) than in the group (n = 4) with a significant increase of temporal muscle activity. The results may indicate that the temporal muscle plays an important role in the perception of static pain in the masticatory system.

Annual review of selected dental literature: report of the Committee on Scientific Investigation of the American Academy of Restorative Dentistry.

The annual review of selected dental literature this year cites 384 published papers and reports. This year's review contains more editorial comment than reviews of years passed. New data on the biological responses to materials is emphasized in several sections. Observations on new compounds able to prevent plaque formation are presented. Clinically relevant advances in knowledge concerning the etching of different tooth structures are reported along with the effect of etching procedures on the dental pulp. Evaluation of periodontal diseases in all age groups is a topic. Limitations of current diagnostic techniques in periodontal disease, temporomandibular disorders, and implant therapy are included. There are new views on the use of dental amalgam. The future use of dental mercury is predicted. Interest in new ceramic systems is indicated as the demand for esthetics continues. Clinical information is emphasized over scientific information throughout this year's review.

Report of the Committee on Scientific Investigation of the American Academy of Restorative Dentistry.

The committee screened several hundred articles, citing 518 published papers. Some are present quality in research, others provide clinical interest, and some are identified as misleading. New techniques in pulp physiology and pathology are reported. Laser use and techniques in prevention, restorative dentistry, and materials use are reported. Epidemiology of selected diseases and the results of various formulations for treatment are cited. Diagnosis of craniomandibular dysfunction is well represented as well as references to literature reviews and other sophisticated scientific investigation. Research on adhesives is presented in respect to bonding agents for dentin and enamel. Several clinical studies are included, along with customary laboratory reports on several materials.

Short-term effect of the stabilization appliance on masticatory muscle activity in myogenous craniomandibular disorder patients.

The short-term effect (4 to 6 weeks) of a stabilization appliance on masticatory muscle activity was investigated in 26 myogenous craniomandibular disorder patients. The patients were instructed to clench at 10% and 50% of their maximum clenching effort in the intercuspal position and on the appliance. Recordings were made before and immediately after appliance delivery, and 2 and 4 weeks after delivery. The average EMG activity of the masseter muscles remained the same during the period of appliance use, whereas the anterior temporal muscles showed an immediate and long-lasting reduction in activity. The appliance also resulted in an improvement in the balance of left and right masseter muscle activity. There was a minor improvement in temporal muscle symmetry at the 50% clenching level and after 4 weeks of appliance use.

The result of treatment of the masticatory system of chronic headache patients.

Fifty-five of 100 chronic headache patients, referred consecutively to a neurologist, exhibited craniomandibular pain during examination of the stomatognathic system. This suggests a possible relationship between the headaches and the condition of the masticatory muscles. The patients were randomly divided into two groups. One group was treated by a neurologist and the other by a dentist. More of the patients treated by the dentist reported a decreased intensity of the headache (P less than 0.025) or a reduction in medication (P less than 0.05). Changes in headache frequency were also reported more often in the craniomandibular disorder treatment group (P less than 0.025).

Craniomandibular disorders in patients with different types of headache.

One hundred recurrent headache patients, referred for neurologic examination, were randomly invited for a functional examination of their stomatognathic system. The patients were grouped on the basis of headache localization, neurologic diagnosis of the headache, and stomatognathic diagnosis. The relationship between groups was analyzed. Several significant correlations were found between the clinical findings and the localization of headache (P less than 0.05 to P less than 0.001). Patients with or without a definite craniomandibular disorder pain displayed differences in mouth opening capacity (P less than 0.001). The results indicate a close relationship between recurrent headache and craniomandibular disorders, independent of the neurologic diagnosis of the headache.

Craniomandibular asymmetry in headache patients.

The stomatognathic system was examined in 100 chronic recurrent headache patients, and the asymmetry in clinical and radiographic findings was studied. A clinically recorded facial asymmetry was found more frequently in patients with a definite CMD pain (P less than 0.001), in patients with mainly a unilateral headache (P less than 0.01), and in patients with a head injury in the history (P less than 0.05). The radiographically determined asymmetry in condylar height in these headache patients was high. More condylar asymmetry was found in migraine patients than in patients with tension headache (P less than 0.05). Asymmetric findings in the hard-tissue condition of the temporomandibular joint were more prevalent in patients with a definite CMD pain and in those with mainly bilateral headaches.

Differences in headache patients regarding response to treatment of the masticatory system.

Twenty-three neurologically examined headache patients completed treatment for a concomitantly diagnosed craniomandibular disorder. More than two-thirds of the subjects responded favorably to the treatment and headaches decreased. Differences between patients regarding the response to treatment were studied. Patients with a decreased headache intensity reported more coexisting neck problems before treatment (P less than 0.05). Patients with an alleviation of headaches showed a larger distance between passive and active maximum mouth opening before treatment (P less than 0.05). The probability of headache improvement by craniomandibular disorder treatment was found to be greater in patients with a difference of 5 mm or more between passive and active maximum mouth opening (P less than 0.05).

Craniomandibular stiffness toward maximum mouth opening in healthy subjects: a clinical and experimental investigation.

A new technique for measuring craniomandibular stiffness during mouth opening to the border position was tested. A small force transducer and a jaw tracking device were used to calculate the stiffness in a healthy group of male and female students. Simultaneous EMG recordings were taken from the masticatory muscles to observe the EMG activity during the experimental tests. The craniomandibular stiffness curves of the male group exhibited a stiffer behavior than those of the female group (P less than 0.05). The clinically obtained "endfeel" distance exhibited a significant correlation with different stiffness sections in the stiffness curves (P less than 0.05). Enhanced muscular involvement during mouth opening to the border position was shown as an increase in the clinical endfeel distance.

Balance in masticatory muscle activity during natural chewing and submaximal clenching.

The balance in the electromyographic (EMG) activities of the left and the right masseter and the left and right anterior temporal muscles during chewing and during submaximal clenching at 10% and 50% of the maximum voluntary contraction in the inter-cuspal position was investigated in twenty healthy adults. Muscular asymmetry patterns during chewing and clenching were positively correlated for both pairs of masticatory muscles investigated at the 50% level (P less than 0.01-P less than 0.001) and for the masseter muscles, also at the 10% level (P less than 0.01). Stronger correlations in muscular asymmetry were found for the masseter muscles and at the higher submaximal clenching level. In general, the masseter muscles displayed a greater degree of asymmetric activity than the anterior temporal muscles during both chewing and clenching (0.05 less than P less than 0.1-P less than 0.025). The average EMG amplitudes of both masseter or both anterior temporal muscles within each subject showed no correlation between clenching and chewing. The correlations between muscular asymmetries observed during static (clenching) and dynamic (chewing) conditions suggest that there are common factors influencing these activities.

The immediate effects of a stabilization splint on the muscular symmetry in the masseter and anterior temporal muscles of patients with a craniomandibular disorder.

In 36 myogenous craniomandibular disorder patients, the immediate effects of a stabilization splint on the symmetry in the activities of the masseter and anterior temporal muscles during submaximal clenching at five clenching levels were investigated electromyographically. After the adjustment of the splint necessary at the time of delivery, 20 splints remained free from occlusal interferences throughout the treatment period and thus needed no further adjustment. These splints caused an immediate improvement in masseter muscle symmetry at the time of delivery (p less than 0.01). However, 16 splints needed further adjustment for occlusal interferences at the first recall, 2 weeks after delivery of the splint. These splints resulted in a small but statistically significant worsening in masseter muscle symmetry at the 10% clenching level (p less than 0.01). No such response was found for temporal muscle activity. The immediate changes in masseter muscle activity suggest that muscular symmetry is an objective basis in the evaluation of the treatment provided.

The recognition of craniomandibular disorders--an evaluation of the most reliable signs and symptoms when screening for CMD.

Two hundred and twenty-two patients who had been examined and treated for craniomandibular disorders were re-evaluated using a screening protocol. This protocol was developed from previous studies which had elucidated the most reliable signs and symptoms of craniomandibular disorders. Unilateral signs and symptoms were found to be more common than bilateral signs and symptoms. Dynamic and static pain tests were shown to be decisive in determining the preliminary diagnosis. There was a significant difference in vertical condylar height asymmetry between those patients diagnosed as having a myogenous and an arthrogenous origin of pain.

The OPG: an aid in TMJ diagnostics. III. A comparison between lateral tomography and dental rotational panoramic radiography (Orthopantomography).

In the comparison of radiographical findings (flattening, irregular surface and osteophyte formation) between lateral tomography and Orthopantomography in thirty-one female patients with craniomandibular disorders, a 76% similarity was found. A trend in the findings was seen: with an increase in radiographical findings visible in the tomograms there is a decrease in the amount of condylar asymmetry visible in the Orthopantomograms and a decrease in the age of the patients.